Flat and rotary die cut dies



Oct. 27, 1970 s, w, QTTQ ETAL 3,535,955

FLAT AND ROTARY DIE CUT DIES Filed Feb. 2l. 1968 2 Sheets-Sheet 1 me@mp/af@ Praxa/e .5ms/Wye /'ne Tem/afg Qyed pressa/'e .5eme/#Ve Ff/m@ef/ec fof Dyed Pressure Sens/7W@ F//m Oct. 27, 1970 s. w. o'r'ro ETAL3,535,955

FLAT AND ROTARY DIE CUT DIES OOOOOO OOOOOO NEY United States Patent Oice 3,535,955 FLAT AND ROTARY DIE CUT DIES Stanley W. Otto, Kansas City,Mo., and Seth W. Warrell, Shawnee Mission, Kaus., assignors to HallmarkCards, Incorporated, Kansas City, Mo., a corporation of Missouri FiledFeb. 21, 1968, Ser. No. 707,217 Int. Cl. G03c 5 /00 U.S. Cl. 76--107 8Claims ABSTRACT F THE DISCLOSURE A method of preparing flat and rotarydie cut dies from a line drawing of a design. Au outline of the linedesign is made on pressure-sensitive film, which upon development isused as a mask over a sheet of metal plate-backed photosensitivematerial during exposure thereof. The line defining area of thephotosensitive material which is hardened during exposure of the sheetpresents a rib projecting from the backing plate upon development of thematerial. A copper matrix is electro-formed against the developedphotosensitive sheet and the grooves formed in the matrix are routedwith a V-shaped cutting tool. A layer of Ni is then electro-formedagainst the routed copper matrix to form the die cut die.

This invention relates to the field of graphic arts and especiallyprocesses and apparatus which significantly improve the preparation ofrotary and flat die cut dies used to cut relatively intricate patternsin various materials such as paper, plastic, or thin metal sheets.

It has long been known that the appearance and visual effect of manyprinted designs, especially on paper stock, or thin sheets of metal orplastic, may be enhanced by the cutting out of an outline of the designso as to emphasize the peripheral edge of the artistic impression on thesheet. The art in this area has become very highly developed inconnection with the production of greeting cards, calendars, paper partygoods, decorative wrapping, and decorative accessories, with the qualityof the die cut margin and its alignment with the printed design areabeing especially critical because of the normally relatively closevisual observation which is made of the design by a recipient orpurchaser of the item.

Heretofore, the die cut operations have been carried out in two majorways, all of which have been time-consuming and expensive insofar as thetooling is concerned. Flat die cut dies have for the most part been madeby first preparing a line drawing of the outline of the design to be diecut followed by securing of the line drawing to a sheet of plywoodapproximately 3A# in thickness. A highly skilled worker than utilizes ajigsaw to cut through the plywood along the line of the design to becut. Next, another workman, using the cut plywood as a guide, prepares abent steel rule of configuration which will fit into the groove formedin the plywood by the jigsaw. A hand-operated bender having a fixed,generally V-shaped mandrel and a shiftable pointed bending force is usedto bend the steel rule transversely thereof in a manner to reproduce theline design image formed in the sawed plywood. Frequently, it isnecessary to employ modified hand-tools in the nature of pliers toproduce bends in the rule of relatively narrow radius. The bent steelrule is then inserted in the plywood and secured therein so that thesharp edge thereof projects above the surface of the wood. Thus, uponmounting of the assembly on a supporting plate, it is ready for use in apress.

It can be appreciated that this procedure not only is extremelytime-consuming but of necessity, involves highly skilled workers whomust spend a long time in apprenticeship before mastering the techniqueof prepar- Patented Oct. 27, 1970 ing a satisfactory die cut die, atleast insofar as the more intricate shapes are concerned.

A second type and the other major procedure for preparing dies involvesthe utilization of tools to machine the surface of a wear-resistantmetal plate so as to form sharp ribs projecting from the major plane ofthe plate which serve as cutters to cut the stock against which the diecut die is forced. In this instance, it is the usual practice to leave aportion of the surface of the machined die to serve as a bearer.Machining operations may be used to fabricate either fiat or rotary diecut dies and, in fact, is the only generally satisfactory method nowavailable for the preparation of rotary cutting dies.

It is, therefore, the primary object of this invention to provide amethod of constructing die cut dies of either the rotary or fiat typewhich substantially eliminates the manual fabrication operations andattendant dependence on skilled workmen which have been requisites ofprior machining and steel rule bending fabrication techniques.

It is a further important object of the invention to provide a method ofpreparing rotary or flat die cut dies which permits reproduction of aline design utilizing electroforming processes so that much of thelaborious manual efforts heretofore involved are obviated in permittingthe use of less skilled personnel without sacrificing the quality of thecutter and, in fact, permitting a more accurate reproduction of thedesign than has heretofore been possible of achievement except only withvery painstaking and expensive procedures.

Another very important object of the invention is to provide a method offabricating a fiat or rotary die cut die in a shorter period of timethan has heretofore been possible and a lower cost by virtue of theutilization of a technique of transferring the design from onereproduction to another without loss in configuration thereof by virtueof the fact that the original design to be die cut in line form istraced onto a pressure-sensitive film toform a clear area thereoncorresponding to the design and which thereby presents a mask throughwhich a photosensitive material carried by a metal plate is exposed andthen developed so that only those areas which are hardened by theexposure process and which correspond to the design remain afterdevelopment of the photosensitive material and thereby permittingforming of a matrix against the developed photosensitive material whichpresents a female of the die so that the die may be formed directlyagainst the matrix. In this connection, a subsidiary object of theinvention is to provide a technique as described wherein the cuttingedge defining rib of the die is relatively sharp at the apex thereofwithout secondary machining or other treatment being required because ofthe fact that the grooves in the matrix are routed out with a V-shapedtool prior to forming of the die therefrom and thus assuring that thecutting edge ribs in the die are truly V-shape in cross section and ofuniform height throughout the extent of the die.

Also an important object of the invention is to provide a method ofpreparing fiat or rotary die cut dies which lends itself to high volumeoperations by virtue of the fact that as many dies as may be needed canbe prepared, either at one time or as the demand therefor arises, andalso permits fabrication of such dies on a production line basis wherevarious individuals do specific jobs in preparation of the die.

An object of the invention is also to provide a procedure for preparingdie cut dies which is adaptable without significant change for thefabrication of either flat or rotary dies by virtue of the fact that theforming techniques are the same in both instances with the onlydifference being the utilization of an optically distorted line drawingas the starting template for rotary die cut dies,

`In the drawings:

FIG. 1 is a plan view of a line template usually cornprising a sheet ofpaper having a line representation thereon of the design to be die cut;

FIG. 2 is a vertical cross-sectional, schematic representation of asheet of pressure-sensitive film overlying the design sheet of FIG. 1and illustrating the Way in which a stylus is employed to develop thefilm to provide an outline of the design;

FIG. 3 is a plan view of the developed lm as illustrated in FIG. 2;

FIG. 4 is a plan view of the film as illustrated in FIG. 3 after dyeingof the opaque areas thereof;

FIG. 5 is a vertical cross-sectional, schematic representation of thedyed film of FIG. 4 used as a mask in overlying relationship to a sheetof photosensitive material supported by a backing plate and illustratinga typical way in which the photosensitive material is exposed to asource of energy rays through the mask;

FIG. 5a is an enlarged view of the circled portion of FIG. 5;

FIG. 6 is a vertical cross-sectional view through the photosensitivematerial after development thereof to remove the portions of thematerial which remain unhardened after exposure to the source of energyrays;

FIG. 7 is a vertical cross-sectional, schematic showing of the developedphotosensitive material backed by a metal plate and illustrating the wayin which a metal matrix is electroformed against the developed face ofthe photosensitive material;

FIG. 7a is an enlarged view of the circled portion of the laminateillustrated in FIG. 7;

FIG. 8 is a vertical cross-sectional, schematic representation showingthe way in which a routing tool is ernployed to route out the bottom ofthe grooves formed in the metal matrix illustrated in FIG. 7, and with ametal plate being used to support the matrix during the routingoperation;

FIG. 8a is an enlarged view of the circled portion of FIG. 8;

FIG. 9 is a vertical cross-sectional, schematic showing of the way inwhich a nickel die is electroformed against the matrix while supportedby a metal plate;

FIG. 10 is a vertical cross-sectional, schematic showing of the way inwhich the nickel die shown in FIG. 9' and supported by a backing membermay be mounted on the platen of a press and ejector material secured tothe cutting face of the die; and

FIG. 11 is a plan view of an electroformed nickel die adapted to besecured to a rotary cylinder and illustrating the way in which thecutting rib is optically distorted for use on a rotary press.

In accordance with the preferred procedure of the invention, a linedrawing is prepared on a sheet of paper 22 to present a line template24. In this instance, it is assumed that a flat die cut die is to beprepared and thus the outline 20 is of the exact shape of the area to becut out of a sheet of material such as thin metal, plastic, or paperstock.

Next, a sheet of pressure-sensitive film 26 is placed over the designsheet or line template 24 while the latter is supported on a planarsurface such as a light table permitting viewing of the line design 20through film 26. The pressure-sensitive film 26 is preferably of thetype having a transparent synthetic resin backing element provided Witha coating thereover presenting a large number of discrete, relativelysmall, pressure-rupturable cells. Upon rupture of the cells, thetranslucent or generally opaque coating is destroyed to an extentwhereby the transparent backup element is fully exposed on both sidesthereof for unimpeded viewing therethrough. Referring to FIG. 2, thefilm 26 is positioned on template 24 in disposition such that therupturable coating lays against the upper face of the design sheet. Aparticularly useful pressure-sensitive film for the present purpose ismanufac- 4 tured and distributed by the Photo Products Department of E.I. du Pont de Nemours & Co., Wilmington, Del., and sold under thetrademark Cronapress.

A stylus is then used to develop the film by tracing along the outlineof design 20` Iwith sufficient pressure to effect rupture of theindividual cells of the coating on the film directly under the point ofthe stylus. Since it is desirable to form as fine a line as possible inthe film, the tip of the stylus should be sufficiently pointed to makeonly a very fine line Without cutting the upper surface of the film.Best results are obtained utilizing a stylus having a somewhat roundedpoint having a diameter of about 0.001.

The developed pressure-sensitive film is illustrated in FIG. 3 whereinit can be seen that the clear section 30 surrounded by the translucentportion 32 conforms to and is of the exact same shape of line design 20.Next, the film 26 is successively subjected to densier and stabilizersolutions which render the remaining emulsion part 32 of film 26 opaque.Suitable densier and stabilizer solutions are also distributed by DuPont under the Cronapress designation. These materials turn theunruptured part of the emulsion 32 a dark blue opaque color which isstabilized by application of the stabilizer solution to the dyedsurface.

The dyed film 26 is placed over a photopolymer sheet 34 having a layerof photosensitive material 36 supported on and firmly affixed to a metalbacking plate 38. A preferred photopolymer sheet is manufactured anddistributed by E. I. Du Pont de Nemours & Co., Wilmington, Del., underthe trademark Dycril. U.S. Pat. No. 3,306,745 describes a photopolymersheet of a usable type in the present process. Dycril is particularlyadvantageous because the layer of photosensitive material 36 is of athickness sufiicient to provide a cutting rib of desired height on thefinal die as will be explained. Normally, the thickness of thephotosensitive layer 36 will be around 0.025.

The laminate illustrated in FIG. 5 comprising the dyedpressure-sensitive film 26 overlying sheet 34 is then exposed to asource of ultraviolet rays preferably constructed so as to direct suchrays through the film 26 onto material 36 in'substantially perpendicularrelationship to the planar surface of the assembly as illustrated inFIG. 5. In this instance, the spaced electrodes 40 and 42 vwhich producean arc `44 are positioned in front of a reflector 46 which serves todirect the ultraviolet rays onto the photosensitive material 36 throughthe clear section 30 of film 26 in essentially straight lines. It is tobe appreciated that in actual practice, the ultraviolet source will bespaced a considerable greater distance away from the photopolymer sheet34 than is indicated only schematically in FIG. 5.

Those parts of sheet 34 directly underlying the clear section 30 of film26 and which are thereby exposed to the ultraviolet rays from the arc44, are caused to undergo further polymerization and thereby hardenwhile the areas of sheet 34 directly under the opaque portion 32 remainessentially unhardened and may be removed by a conventional alkalinewash solution distributed by Du Pont in connection with its Dycrilmaterial.

FIG. 6 illustrates the photopolymer sheet 34 after development thereofwith an alkaline wash solution as described whereby the unhardenedportions of the material 36 are Washed away by the Solution leaving onlythe hardened or polymerized design defining ribs 48 in the surface ofmaterial 36 facing away from plate 38.

In this connection, it is to be understood that a part of the material36 affixed directly to plate 38 is sufficiently hardened duringprocessing of the original photopolymer sheet to render the sameresistant to being washed away by the development solution so that evenafter the Washing operation a thin layer of the photopolymer materialremains on plate 38 as illustrated in FIG. 6. In addition, and as bestshown in FIG. 7a, the design defining rib 48 projecting from the modeledsurface of the photopolymer sheet 34 is defined by a pair of divergingwall surfaces 50 and 52 which merge with the remaining layer ofphotosensitive material 36 on plate 38. The outer extremity of rib 48which is represented by a somewhat flat margin S4 in FIG. 7a, is of atransverse width substantially equal to the width of the design definingsection 30 of developed film 26. However, the thickness of the rib 48transversely thereof between margin 54 and the remaining layer ofphotosensitive material 36 increases as the plate 38 is approachedbecause of the fact that even though the ultraviolet rays from arc 44are directed onto the laminate of FIG. 5 in substantially straight linesperpendicular to the planar surfaces thereof, the energy rays passingthrough clear section 30 and penetrating the layer of material 36 strikethe upper face of plate 38 and are reflected -back into the photopolymermaterial. As a consequence, an area of the photopolymer material whichis essentially trapezoidal in cross section is caused to undergo furtherpolymerization and is of the shape best shown in FIG. 7a. Thisphenomenon is important to the present process since it assuresproduction of a final die wherein the cutting rib assumes substantiallythe shape of rib 48 and is thus of sufficient structural integrity towithstand the wear encounted in long-run die cutting operations.

Next, the modeled surface of the photopolymer sheet 34 is coated with aparting agent which is electrically conductive [c g., colloidal orprecipitated silver] and a layer 56 of copper is electroformed againstthe coated surface of photopolymer sheet 34. The layer of copper therebydefines a matrix 58 which is essentially a female of the developedphotopolymer sheet 34. As best shown in FIG. 7a, the matrix 58 therebyhas grooves 60 in one face 62 thereof which correspond with ribs 48 ofphotopolymer sheet 34. Because of the fact that the lower part of eachof the grooves 60 is also somewhat at because of the conformation tomargin 54 of rib 48, it is desirable that the grooves 60 to be routedwith a V-shaped cutting tool to cause the grooves to be truly V-shapedin cross section and of uniform depth throughout the extent thereof.

Before carrying out the routing operation however, it is desirable tomount the copper matrix 58 on a steel backing plate 64 through the useof a suitable adhesive such as an epoxy resin 66. Securing of the matrix58 to plate 64 is carried out so that the planar surfaces of the membersare maintained in parallel relationship and with the face 62 facingupwardly as shown in FIG. 8.

The routing of matrix 58 is preferably carried out by utilization of acutting tool 68 having a V-shaped cutting edge 7u and which is rotatablein a spindle sleeve 72 provided with an adjustable depth-limitingcylinder 74 on the lower extremity thereof. It is to be appreciated thatthe spindle sleeve 72 is carried by the support therefor in such amanner that, although being movable vertically, the axis of tool `68 ismaintained exactly perpendicular to the face 62 of matrix 58.Furthermore, the cylinder 74 is adjustable on sleeve 72 so that uponengagement of the lower circular edge of cylinder 74 with the face y62of matrix 58, the cutting edge 70 of tool 68 is received in groove 60such that the angled edges of the tool are exactly parallel with theinclined walls defining the respective portions of grooves 60. In thisway, not only is the groove 60 routed out so that it is of preciseV-shaped configuration, but the depth of such groove is uniformthroughout the extent of the matrix. The tool holder may form a part ofa milling machine so that the operator can control the movement thereofacross the matrix face 62, or in the alternative, a milling pantographused wherein the stylus thereof is moved along the design of sheet 24 orin a sheet of material having an intaglio relief therein deining design20.

After routing of the matrix 58, a parting agent which is electricallyconductive as noted above is placed over the face 62 thereof in coveringrelationship thereto and a layer 76 of nickel electrodeposited againstthe copper 56 as best shown in FIG. 9. U-pon removal of theelectroformed layers 76 from matrix 58, the back portion 78 thereof ismachined to the level 80` illustrated by dotted lines in FIG. 9 so thatthe remaining back face 82 of the nickel 76 is essentially at andparallel with the front face of the nickel. The member thus presentedcomprises a nickel die 84 which is adapted to be mounted on press platen86 lusing a contact adhesive 88. The extent of milling or machining ofthe back portion of nickel layer 76 is determined by the depth of thegrooves 90 which are formed in the electrodeposited nickel duringelectroforming thereof. The milling should be carried out to asufficient extent to cause the remaining back face 82 of die 84 to beat.

Foam material 92 may be aixed to the cutting face of die 84 andpreferably is slightly higher than the cutting ribs 94 projecting fromthe face 96 of die 84 so that when the latter is brought down intoengagement with the cutting plate `98 on lower press platen 100, theejector material 92 will serve to displace the cut stock from die 84.

The ribs 94 projecting Afrom face 96 of die 84 have a sharp loutercutting edge and such edge not only conforms exactly to the design 20but is of also uniform height above the level of face 96. Bearers 102which are a conventional part of a die cutting machine serve to limitthe extent of reciprocation of die 84 toward cutting plate 98.

Although the preferred process described above suggests electroformingof matrix S8 against the developed photopolymer sheet 34 followed byelectroforming of the nickel die 84 against matrix 58, it is to beunderstood that various techniques may be effected for fabrication ofthese components. For example, a phenolic synthetic resin matrix may bemolded against sheet 34 and the nickel die 84 then electroformed againstthe synthetic resin matrix. Alternatively, the die 84 may be formed bygas plating techniques utilizing nickel tetracarbonyl Ni(CO)4 as thecomposition from Which the nickel is deposited. Similarly, gas platingmay be used to form matrix 58.

The present process is equally adaptable for preparation of rotary diecut dies, although the specific steps thus far set rforth have relatedspecifically to the fabrication of a flat die cut die 84. The principaladditional steps required involve photographically reproducing the linetemplate 24 so that the line design 20v thereon is optically distortedin a known manner so that when the design is reproduced on a memberwhich is adapted to be wrapped around a cylinder forming a part of arotary press, the design cutout of a flat sheet passed therebetween willconform to the original design 20 rather than be distorted. In addition,the nickel layer 76, gas plated 0r electroformed against matrix 58,should be of a thickness lending the same to be bent around a cylinderof a rotary press without cracking. In this respect, the rear surface ofthe electroformed or gas plated nickel may be backed up with a suitablematerial or machined away as necessary to provide a flat rear face. Atypical, initially flat die cut die is illustrated in FIG. ll anddesignated by the numeral 184, with it being noted that the rib 194projecting from the face 196 thereof is optically distorted withreference to the design 20 so that when the die 184 is wrapped around acylinder, there will be no distortion of the design cut in the stockpassed between the die and a backing cylinder. Furthermore, the opposedends of die 184 are blanked and pierced as indicated to facilitatemounting of the cutting member on the rotary machine.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. A method of constructing a die cut die having a rib portionprojecting from one surface thereof and presenting a cutting edgeconforming to the shape of a line design, said method including thesteps of:

preparing a mask for use against a sheet of photosensitive material,said mask having an area which is substantially opaque to energy rayscapable of effecting hardening of the photosensitive material, and aline defining section within said area capable of permitting passage ofsaid energy rays therethrough and conforming to the configuration ofsaid design; positioning the mask over the sheet of said photosensitivematerial wherein the latter is of a thickness exceeding that of thestock to be cut with said die and of a depth at least approximatelyequal to the height of the rib desired in the final die cut die;

exposing the assembly of said sheet and the mask to said energy rays fora period sufficient to effect hardening of the transversely trapezoidalline defining portions of the photosensitive material underlying saidsection of the mask;

developing the exposed sheet to remove the unhardened portions thereof;fabricating a matrix of the developed sheet and having design defininggrooves in the face thereof against the sheet of photosensitivematerial; and

electroforming a layer of wear resistant metal over the matrix to formsaid die.

2. A method as set forth in claim 1, wherein is included the step ofrouting out the bottom of the design defining grooves in said matrix tocause the inner part of each of the grooves to be of substantiallyV-shaped configuration.

3. A method as set forth in claim 2, wherein said routing of the matrixincludes the steps of passing a tool along said grooves having aV-shaped cutting edge, and maintaining the tool at a predetermined depthin said grooves during movement thereof.

4. A method as set forth in claim 1, wherein preparation of the maskincludes the steps of placing a pressuresensitive lrn on a supporttherefor, said film having the characteristics of normally beingsubstantially nontransparent but subject to being converted totransparent form in those areas where pressure is applied thereto whilesupport is provided for such lm, and applying suicient force to saidfilm to effect conversion thereof along a line substantially conformingto the shape of said design.

5. A method as set forth in claim 4, wherein is included the step ofapplying said line defining force to a film comprising a transparentbacking element provided with a coating on one face thereof having alarge number of relatively small, pressure rupturable cells therein.

6. A method as set forth in claim 5, wherein is included the step ofplacing a pointed tool against the coated surface of said element andmoving such tool across the coated surface with sufficient force beingapplied thereto to effect rupture of said cells in a pattern presentingsaid design.

7. A method as set forth in claim 4, wherein is included the step ofdyeing the remaining nontransparent portions of the film to present saidopaque area thereof.

8. A method as set forth in claim 4, wherein is included the steps ofpreparing a line drawing of said design, placing the pressure-sensitivefilm over the line drawing, providing a generally planar support for thedrawing and said lrn, and tracing the outline of the design on the filmby placing a pointed tool against the film at a point in overlyingrelationship to the design followed by movement of the tool across thefilm under sufficient pressure to effect conversion of the lm.

References Cited UNITED STATES PATENTS 1,947,916 2/1934 Mitchell 96-36t3X 1,986,637 1/1935 LHollier 204-4 X 3,306,745 2/1967 Webers 96-35.13,341,329 9/1967 Blake 96-36 3,367,215 2/1968 Rice et al. 76-107 THERONE. CONDON, Primary Examiner H, A. KILBY, JR., Assistant Examiner U.S.Cl. X.R. 96-36

